The present invention relates to improved insecticide compositions and to devices containing such compositions for controlling insect populations, and more specifically, to aqueous based insecticidal compositions adaptable for application to substrates by highly efficient and economical printing means to provide improved insect traps, pest strips, tapes and ribbons, sheets, and the like.
Chagas' disease is the most common form of trypanosomiasis in the Americas. An estimated 65 million people are at risk, and an estimated 20 million people are currently infected with the disease. It is commonly transmitted by large, blood-sucking triatomine (assassin) bugs from Venezuela, Rhodnius prolixus. This and other species of triatomids live in the roofs and walls of dwellings of the poor throughout South and Central America. The assassin bugs prefer structures which provide shelter for them. They include structures made of adobe, bahareque, a building technique using woven twigs, leaves and mud; wood and poorly constructed concrete blocks.
The causative agent of Chagas' disease, Trypanosoma cruzi, lives in the blood of its human victims and of the rodents and marsupials commonly found in rural areas. It is ingested by the assassin bug as part of its blood meal. The parasite passes through the bug's digestive tract, and is deposited in its feces and then on the skin of its victim. The parasite eventually enters the circulatory system either by being scratched into a wound or through the eyes whereupon it attacks the tissues of various organs, and particularly the heart, eventually causing death of the host.
International and national public health strategies have emphasized eradicating or controlling insect vectors in order to minimize the spread of disease. Since the 1940's, the effectiveness of this strategy has depended upon the widespread use of chemical pesticides. It was once expected that pesticides alone would be sufficient to eliminate the threat of major insect-born diseases. Reliance on such a highly specialized strategy has for some time been questioned because of the problems it has caused, e.g. unintentional extermination of beneficial species, accelerated mutation of resistance to chemicals in vectors, lingering environmental pollution causing secondary public health problems, inflationary costs representing a financial drain on the fragile economies of developing nations and on the limited budgets of international agencies, and chronic organizational and bureaucratic problems which have inhibited effective delivery of services to affected populations.
In Venezuela, for example, the government's approach to building and renovating housing has been ineffective both socially and structurally. Reports indicate that some of the effectiveness of chemical sprays was neutralized within a short time period because of the lime content of white-washed walls of rural houses. The concrete block material used in new building construction fractured in a short period of two years. This, along with poor traditional construction methods, help to provide increased breeding grounds for the vector. Hence, although chemical means remain an important part of the strategies for controlling disease vectors, alternative lower cost, environmentally safe means are needed for controlling insect populations, particularly those associated with the transmission of disease. Such alternatives have been limited, e.g. by the previously unpredictable behavior which reduced the effectiveness of proposed traps.